The present invention is directed, in general, to computer networks and, more specifically, to a link layer device, method of translating packets between transport protocols and a packet transport system employing the device and method.
Packet transport systems, such as Asynchronous Transfer Mode (ATM) systems, employ a technique of disassembling information at a sending end of a communications network for insertion into separate packets of data and reassembling the same information from the data packets at a receiving end of the communications network. Communications networks employing this technique are especially advantageous in common carrier or time-shared switching networks, since a communication path or circuit for packet transmission associated with a user""s message is only employed while each packet is being forwarded through the communications network. The communication path is, therefore, available to other users or for other communication traffic during intervening periods.
The packet transport systems are capable of providing integrated information transport services for a wide range of applications (e.g., interactive data, bulk data, signaling, packetized voice, image). Instead of designing specialized networks optimized for specific applications, many services can be simultaneously supported over the same path to the switching network. User information of varying types is converted into packets, and the switching network transports the packets between users. Instead of being tied to fixed rate connections, the switching network adapts the connection rates to the particular needs of the end users. Furthermore, it is possible to create a uniform user-network interface that is applicable to a broad range of services.
The presently available packet transport systems, however, can only handle a limited number of channels associated with the switching network. The systems are restricted by the transmission protocol and the ability of the packet transport systems to accommodate a large number of channels without dropping a large number of packets.
Accordingly, what is needed in the art is a system for transporting packets over a packet transport network that may accommodate a large number of channels and overcomes the deficiencies of the prior art.
To address the above-discussed deficiencies of the prior art, the present invention provides, for use with a packet transport network having first and second packet networks employing first and second transport protocols, respectively, a link layer device, method of translating packets between transport protocols and a packet transport system employing the device and method. In one embodiment, the link layer device includes a first protocol subsystem that receives and transmits packets in the first transport protocol over the first packet network. The link layer device further includes a physical layer device subsystem coupled to a physical layer device associated with the link layer device. The physical layer device subsystem translates the packets between the first and second transport protocols and communicates with the physical layer device employing flow control. The link layer device still further includes a channel memory subsystem, associated with the first protocol subsystem and the physical layer device subsystem, that buffers the packets in a channel storage area on a per channel basis for transmission by the link layer device over one of the first and second packet networks.
The second protocol includes a packet control status with a channel number indicator that accommodates a channel number greater than 256. The packet control status allows the link layer device to manage communications with the second packet network via the physical layer device. The channel number indicator indicates which channel connected to the physical layer device the packet is associated with. In a related embodiment, the channel number indicator is of a type selected from the group consisting of: (1) a 16-bit indicator, (2) a 32-bit indicator and (3) a 64-bit indicator. The maximum number that can be represented by the bit size of the channel number indicator specifies the number of possible channels that can be managed by the link layer device. For example, a 16-bit indicator can represent 65,536 channels. Thus, a link layer device that can manage a large number of channels reduces the number of link layer devices employed for large channel applications.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.